1. Field of the Invention
The present invention relates to a joined article and a die for forming a honeycomb structure. More particularly, it relates to a joined article and a die for forming a honeycomb structure in which the lowering of strength around a joining interface is prevented.
2. Description of the Related Art
Heretofore, a joined article of a tungsten carbide base cemented carbide and a stainless steel is used in a die for forming a ceramic honeycomb structure (a honeycomb structure forming die), a precision mold, a die, a plug and the like.
As the honeycomb structure forming die, for example, there is used a die including a joined article (a die base member) obtained by joining a plate-like member made of the stainless steel and provided with back holes for introducing a forming material, and a plate-like member made of the tungsten carbide base cemented carbide and provided with slits connected to the back holes to form the forming material into a lattice-like shape (e.g., see JP-A-2006-051682 and JP-A-2007-181976).
In the honeycomb structure forming die, one surface of the die base member is usually provided with the slits each having a width corresponding to the thickness of each partition wall of a honeycomb structure and having a lattice-like shape or the like, and the opposite surface (the other surface) thereof is provided with the back holes connected to the slits and having large open areas. Moreover, the back holes are usually provided in positions where the slits intersect with one another (e.g., the intersecting positions of the formed lattice-like slits), and both the back holes and the slits arc connected to one another in the die base member. Therefore, a forming material such as a ceramic material introduced from the back holes moves from the back holes having comparatively large inner diameters to the narrow slits, and is extruded as a formed honeycomb structure article from openings of the slits. Thus, slit portions are narrow, and hence a high pressure is applied to the slit portions when the ceramic material passes through the slit portions, whereby the slit portions have an easily worn structure. On the other hand, in the honeycomb structure forming die including the slits formed in the member made of the tungsten carbide base cemented carbide having a high wear resistance, the tungsten carbide base cemented carbide is used to improve the wear resistance.